Automatic matrix cleaner



1965 c. P. WILLIAMS ETAL 3,

AUTOMATIC MATRIX CLEANER Original Filed Oct. 1, 1962 2 Sheets-Sheet 1 INVENTORS CARL P WILLIAMS OZIEL H HEITT Jan. 5, 1965 C. P. WILLIAMS ETAL AUTOMATIC MATRIX CLEANER Original Filed Oct. 1, 1962 2 Sheets-Sheet 2 INVENTORS CARL F? WILLIAMS OZIEL H. HEITT United States Patent 3,163,962 AUTUMATEC MATRIX CLEANER Carl F. Williams, R0. Box 561, and Oziel H. Heitt, 7146 N. th Drive, both of Glendale, Ariz. Continuation of application Ser. No. 227,174, (Dot. 1, 1962. This application Aug. 12, 1963, Ser. No. 313,138 14 Claims. (Cl. 51-9) This invention relates to an abrasive cleaning device and, more particularly, to an abrasive cleaning device useful in cleaning the matrix of an automobile tire retreading or recapping mold.

This application is a continuation of our copending application, Serial No. 227,174, filed October 1, 1962, now abandoned.

In the art of recapping or retreading automobile tires, it has been a problem to clean the mold matrix from time to time in order to remove deposits from the matrix which normally results during the retreading or recapping process. Such deposits tend to cause undesirable surface effects on the retreads or recaps produced in such a mold and, therefore, it is desired to maintain a mold matrix in clean condition so that undesirable imprints from deposits in the matrix are not imposed upon the retread or recap formed in the mold.

Due to the intricate recesses and designs in a tire retreading mold matrix, it is extremely difficult to clean these structures manually. Furthermore, ordinary abrasive blasting of these surfaces cannot be accomplished in an open area and, consequently, must be enclosed to prevent dispersion and loss of the abrasive materials being used.

It has been found that either glass beads, sand, or any other suitable granular material may be used as an abrasive material for cleaning mold matrices when such materials are propelled pneumatically into the various surfaces of the tread forming structure of the matrix.

It has been a problem to contain various abrasive material in the enclosure of a machine and to impel these abrasive materials in a circuit so that they are reusable and not lost and to provide pneumatic flow from an impeller to propel such abrasive materials without running these abrasive materials through the impeller.

Glass beads, when used in lieu of sand, or other material, may efliciently clean mold matrix structures, however, these beads are more expensive than sand and, therefore, it is important that these beads not be lost during the cleaning of a matrix thereby.

Accordingly, it is an object of the present invention to provide an abrasive cleaning device particularly adapted for use in cleaning the matrix of an automobile tire retreading or recapping mold.

Another object of the invention is to provide an abrasive cleaning device comprising fully automatic means contained in a housing for the pneumatic projection of abrasive materials into a mold matrix and for rotating the same so that the matrix is efficiently cleaned by a pneumatic blast which projects abrasive materials into all of the detailed cavities of the matrix.

Another object of the invention is to provide an abrasive cleaning device particularly adapted to contain a matrix of an automobile tire retreading or recapping mold in a housing wherein abrasive materials are projected into the matrix and fully contained in and around a blower mechanism without losing the materials from the housing and without passing such abrasive materials through the blower of the device.

Another object of the invention is to provide a novel abrasive cleaning device particularly adapted for use in cleaning matrix of automobile tire retreading and recapping molds wherein novel structure is provided for the entrance of air into the blower of the device internally of the abrasive-containing housing and for the exhaust of such air from said housing without carrying any of the abrasive materials away from said housing.

Another object of the invention is to provide an abrasive cleaning device having a housing wherein abrasive materials are contained and wherein a novel abrasive screeding and leveling device disposes the surface ofthe abrasive materials such that these materials may readily be aspirated through nozzles by air from a blower located within the housing; said blower being a centrifugal blower disposed to receive air from the outside of the housing and thus, protected from abrasion by the abrasive materials used in the device.

Another object of the invention is to provide a novel abrasive cleaning device comprising a housing wherein various abrasive materials may be used and projected pneumatically by a centrifugal blower and wherein novel shield means is used centrally of a mold matrix being cleaned in order to control recirculation of coarse or fine abrasive materials and including dust so that these materials and/ or dust do not escape from the housing.

Other objects and advantages of the. invention may be apparent from the following specification, appended claims, and accompanying drawings, in which:

FIGURE 1 is a top or plan view of an abrasive cleaning device, in accordance with the present invention, showing the cover and shield means removed therefrom and illustrating parts and portions broken away and in section to amplify the illustration;

FIGURE 2 is an enlarged fragmentary sectional view taken from the line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged vertical or axial sectional view taken from the line 33 of FIGURE 1; and

FIGURE 4 is a fragmentary sectional view similar to FIGURE 3 but showing a modification of baffle means of the device for controlling the flow of fine abrasive or dust relative to the inlet of the blower of the device.

As shown in FIGURE 3 of the drawings, the abrasive cleaning device of the present invention is provided with a frame 10 having legs 12 adapted to rest on the ground or on a floor. Centrally of this frame 10 is a bearing housing 14 having an upwardly extending spindle 16 on which a blower housing 18 is stationarily mounted by means of a short cylindrical housing section 20.

Mounted on the spindle 16 are bearings 22 which carry a bearing hub 24 of a main housing 2.6. The main housing 25 is thus rotatable about the spindle 16 and supported on the bearings 22. A pulley 28 on the bottom of the main housing 26 is engaged by a belt 30 which also engages a pulley 32 driven by a reduction gear mechanism 34 on one end of a drive motor 36.

The pulley 32 is thus driven at very low speed and its size, relative [to the large diameter of the pulley 28, causes the housing 26 to rotate at very low speed around the axis of the spindle 16 and bearings 22.

The motor 36 is also provided with a high speed output shaft 38 carrying a pulley 40 engaged by a belt 42 which drives a pulley 44 on a blower operating shaft 46. This blower operating shaft 46 is mounted rotatably in bearings 48 and 50. The bearing 48 being in the lower portion of the bearing housing 14 and the bearing 50 being in the upper region of the shaft 46 and supported by the cylindrical housing section 20, hereinbefore described. The shaft 46, at its upper end, is fixed. to a centrifugal impeller 52 mounted in the housing 18. This housing 18, 'as hereinbefore described, is stationarily mounted on the housing section 20 which is fixed to the spindle 16 of the bearing housing 14, which in turn is stationan'ly mounted on the frame 10.

The blower housing 18 is provided with a central inlet 54 and is provided with centrifugal outlets 56 and 58 Patented Jan. 5., 1955 which deliver compressed air to nozzles fill and 62, respectively. Coupled to these nozzles 64) and 52 are aspirator tubes 64 and 68 having lower ends 70 and 72, respectively, which pick up abrasive material 74 lying in a layer on the bottom 76 of the housing 26. The nozzle 60 is provided with an adjustable rubber sleeve 78 which may be adjusted to project pneumatically carried abrasive into the tread forming area 80 of a the mold matrix structure 82, shown in FIGURE 3 of the drawings. The nozzle 62 is provided with an adjustable rubber cylindrical outlet section 84 disposed to project compressed air and abrasive material in a side wall area 36 of the matrix structure 82 and also this nozzle 84 generally may project abrasive material over the entire inner area of the matrix structure, in accordance with its adjustability, as indicated by broken lines in FIGURE 1 of the drawings. The aspirator tube 68 communicating with the nozzle 62 is provided with rake fingers 83 surrounding the inlet opening 72. These fingers 88 being disposed to rake the sand or abrasive at its upper surface into ridges so that air, aspirated through the aspirator tube 68, will carry a substantial amount of sand upwardly into the nozzle tube 62, as will be hereinafter described.

A leveler or screed bar 96 is supported by the housing 18 and levels the sand or abrasive as the housing 26 rotates relative to the housing 18. Thus, the upper surface of the sand or abrasive 74 is disposed at a proper level with respect to the lower ends or the inlet ends 70 and 72 of the aspirator tubes 64 and 68.

At the transition of the aspirator tube 68 and nozzle tube 62, an inwardly extending tab 92 projects into the air stream passing through the nozzle 62, creating a low pressure area in the end of the aspirator tube 68, thereby creating a substantial partial vacuum in the aspirator tube 68 to cause a substantial amount of sand or abrasive material or glass beads to be entrained in the air which passes through the rake fingers 83 and upwardly through the aspirator tube 68. This structure may differ from that of the inlet '70 of the aspirator tube ea since it may in some instances be a smooth ended tube, as shown in FIGURE 3. When it does not employ the rake fingers 88 it picks up a relatively small amount of sand or abrasive material as compared to that picked up when the fingers 88 are utilized. It Will be appreciated that the nozzle 78 thus projects less sand or abrasive material or glass beads than does the nozzle 84, due to the fact that the nozzle 7 8 may be more specifically directed to particular areas while the nozzle 84 may cover a wider range of area internally of the matrix 82.

The matrix 32 rests upon spaced radial fingers 94 which are connected to an inner side wall 6 of the housing 26. The periphery of the matrix 82 is thus spaced from the side wall 96 and the fingers 94 are spaced apart so that there is a substantial open area around the periphery of the matrix 82 to allow for deceleration of pneumatically projected abrasive material or beads so that the material may readily settle to the bottom of the housing 26, later to be picked up and pneumatically projected by the nozzles 66 and 62.

The inlet 54 of the blower housing 18 is provided with a cylindrical structure or pipe section 98 which projects upwardly to a level near the plane of the fingers 94. Telescopically mounted in this pipe section 93 is another pipe section 160 which projects upwardly internally of an opening 192 in a cover 104 removably connected to the upper end of the housing 26 by a conventional bayonet locking mechanism 106. It will be noted that the opening 102 is substantially larger than the outside diameter of the pipe section 160 to permit air to be exhausted from the housing concurrently as air is drawn through the pipe 1% into the inlet of the blower 52.

A bathe plate 197 at its periphery 1% rests on the matrix 82 and surrounds the pipe tilt}. This structure being used to prevent abrasive material, such as sand, from entering the blower 52. These heavy abrasive mateii. rials are prevented from entering the inlet of the blower 52 by means of the pipe 1% and the baffle 107.

When glass beads or lighter materials, including dust, are used in the machine for polishing or finishing the surfaces of the matrix 82, the modification shown in FIG- URE 4 is utilized. This structure comprises a cup-shaped plate 110 having a central opening 112 which is smaller than a central opening 162 being slightly larger than the diameter of the inlet pipe 100.

The cup-shaped plate llll, having a small opening 112 as compared to the opening 1232, is used to control the flow of glass beads and dust in the machine.

When such light abrasive materials we used, air entering the inlet pipe 93 carries dust in the upper part of the housing through the blower 52 and the downwardly projecting annular portion of the cup-shaped plate 118 prevents large particles from escaping from the casing 26.

Thus, it will be appreciated that the cup-shaped baffle 11% is utilized when glass beads are employed in lieu of heavy abrasive materials. These glass bead cleaning materials include lightweight particles and dust, all of which must be returned to the lower portion of the housing and during this operation, the inlet tube is removed so that all of the air entering the opening 102 passes downwardly through the inlet of the blower 52 and thereby prevents dust or fine particles from escaping from the opening 102. While there is a counterfiow operation through the opening 1%, the removal of the pipe 10-0 and the placement of the cup-shaped bafiie has been found efiective in the prevention of fine material from escaping from the opening 1&2 during operation of the abrasive cleaning device of the invention.

It will be appreciated by those skilled in the art that heavy abrasive materials, such as sand, may be used initially to clean the internal surface of the matrix 82 while the lighter abrasives, such as glass beads, or other light materials, may be used for finishing and polishing the matrix surfaces.

A screen 116 is used at the inlet of the blower 52 so that large particles or objects cannot inadvertently be dropped into the blower 52 and damage the blades thereof It will be obvious to those skilled in the art that various modifications of the present invention may be resorted to in a manner limited only by a just interpretation of the following claims.

We claim:

1. In an abrasive cleaning device the combination of: a frame; a main housing thereon; an impeller housing therein and having an air inlet; and impeller in said impeller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; and means for rotating said impeller at a relatively high speed in said impeller housing.

2. In an abrasive cleaning device the combination of a frame; a main housing thereon; an impeller housing therein and having an air inlet; an impeller in said impeller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; and means for rotating said impeller at a relatively high speed in said impeller housing; rake fingers projecting from said aspirator tube means adjacent said open end thereof; said rake fingers disposed to project into said abrasive at said surface level to form ridges in said abrasive and thereby assist aspiration of said abrasive into said nozzle means via said aspirtor tube means.

3. In an abrasive cleaning device the combination of: a frame; a main housing thereon; an impeller housing therein and having an air inlet; an impeller in said impeller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said between; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; and means for rotating said impeller at a relatively high speed in said impeller housing; means forming a transition between said nozzle means and said aspirator tube means to create a low pressure or partial vacuum in said aspirator tube means.

4. In an abrasive cleaning device the combination of: a frame; a main housing thereon; an impeller housing therein and having an air inlet; an impeller in said impeller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; and means for rotating said impeller at a relatively high speed in said impeller housing; means forming a transition between said nozzle means and said aspirator tube means to create a low pressure or partial vacuum in said aspirator tube means; said last mentioned means comprising a member projecting from said aspirator tube means into said nozzle means.

5. In an abrasive cleaning device the combination of: a frame; a main housing thereon; an impeller housing therein and having an air inlet; and impeller in said impeller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; and means for rotating said impeller at a relatively high speed in said impeller housing; said inlet of said impeller housing being disposed to communicate with the center of said impeller; a cover removably secured on top of said main housing and having an opening therein; and an impeller housing inlet tube of smaller diameter than said last mentioned opening and concentric therewith whereby air passing into said inlet tube to said impeller housing may subsequently escape from said main housing through said opening in said cover, whereby dust tending to escape from said housing is carried into said inlet tube.

6. In an abrasive cleaning device the combination of: a frame; a main housing thereon; an impeller housing therein and having an air inlet; an impeller in said impeller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; and means for rotating said impeller at a relatively high speed in said impeller housing; said support means comprising spaced fingers extending inwardly from the sides of said main housing and adapted to support a circular tire mold matrix thereon in concentric relation with said inlet tube and outwardly of said nozzle means.

7. In an abrasive cleaning device the combination of: a frame; a main housing thereon; an impeller housing therein and having an m'r inlet; an impeller in said im peller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; means for rotating said impeller at a relatively high speed in said impeller housing; said support means comprising spaced fingers extending inwardly from the sides of said main housing and adapted to support a circular tire mold matrix thereon in concentric relation with said inlet tube and outwardly of said nozzle means; a flexible and adjustable outlet structure on said nozzle means for adjustably directing flow from said nozzle meansinto said matrix.

8. In an abrasive cleaning device the combination of: a frame; a main housing thereon; an impeller housing therein and having an air inlet; an impeller in said impeller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; and means for rotating said impeller at a relatively high speed in said impeller housing; said support means comprising spaced fingers extending inwardly from the sides of said main housing and adapted to support a circular tire mold matrix thereon in concentric relation with said inlet tube and outwardly of said nozzle means; a second cover plate adapted to be disposed on an upper and outer side of said matrix, said second cover plate having an opening therein concentric with said air inlet tube of said impeller housing.

9. In an abrasive cleaning device the combination of: a frame; a main housing thereon; an impeller housing therein and having an air inlet; an impeller in said impeller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having a open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; and means for rotating said impeller at a relartively high speed in said impeller housing; said support means comprising spaced fingers extending inwardly from the sides of said main housing and adapted to support a circular tire mold matrix thereon in concentric relation with said inlet tube and outwardly of said nozzle means; a second cover plate adapted to be disposed on an upper and outer side of said matrix, said second cover plate having an opening therein concentric with said air inlet tube of said impeller housing; an inverted cupshaped member adapted to be disposed on the lower side of said second cover plate in concentric relation with said opening therein and adapted to prevent the entrance of abrasive materials into said inlet tube when disposed at substantially a level with said matrix.

10. In an abrasive cleaning device the combination of: a frame; a main housing thereon; an impeller housing therein and having an air inlet; an impeller in said impeller housing; a bottom of said main housing adapted to support abrasive material thereon; a bar carried by said impeller housing and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting one of said housings rotatably relative to the other; nozzle means forming outlets for said impeller housing; aspirator tube means communicating with said nozzle means and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle means; means for driving one of said housings rotatably at a low speed relative to the other housing; and means for rotating said impeller at a relatively high speed in said impeller housing; said nozzle means of said impeller housing comprising a pair of nozzles directed substantially 180 degrees apart, one of said nozzle means being provided with aspirator structure adapted to create a relatively lower pressure area therein than the other, whereby one of said nozzle means is adapted to project more abrasive in the air flow into said respective nozzle means than the other.

11. In an abrasive cleaning device the combination of: a frame; a main housing thereon; a nozzle means therein having an air inlet; an air impeller disposed to deliver air to said nozzle means; a bottom of said main housing adapted to support abrasive material thereon; a bar coupled to said nozzle means and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting said housing and said nozzle means rotatably relative to the other; a nozzle forming an outlet for said nozzle means; an aspirator tube communicating with said nozzle and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle; drive means for causing relative rotation between said housing and said nozzle means; and means for rotating said impeller to force air through said nozzle means.

12. In an abrasive cleaning device the combination of: a frame; a main housing thereon; a nozzle means therein having an air inlet; an air impeller disposed to deliver air to said nozzle means; a bottom of said main housing adapted to support abrasive material thereon; a bar coupled to said nozzle means and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting said housing and said nozzle means rotatably relative to the other; a nozzle forming an outlet for said nozzle means; an aspirator tube communicating with said nozzle and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for bolding articles to be cleaned outwardly of said nozzle; drive means for causing relative rotation between said housing and said nozzle means; and means for rotating said impeller to force air through said nozzle means; rake fingers projecting from said aspirator tube means adjacent said open end thereof; said rake fingers disposed to project into said abrasive at said surface level to form ridges in said abrasive and thereby assist aspiration of said abrasive into said nozzle means via said aspirator tube means.

13. In an abrasive cleaning device the combination of: a frame; a main housing thereon; a nozzle means therein having an air inlet; an air impeller disposed to deliver air to said nozzle means; a bottom of said main housing adapted to support abrasive material thereon; a bar coupled to said nozzle means and disposed to screed and level abrasive material to a predetermined surface level above said bottom; means mounting said housing and said nozzle means rotatably relative to the other; a nozzle forming an outlet for said nozzle means; an aspirator tube communicating with said nozzle and having an open portion carried in close proximity to said surface level of said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle; drive means for causing relative rotation between said housing and said nozzle means; and means for rotating said impeller to force air through said nozzle means; means forming a transition between said nozzle and said aspirator tube means to create a low pressure or partial vacuum in said aspirator tube means.

14. In an abrasive cleaning device the combination of: a frame; a main housing thereon; a nozzle means therein having an air inlet; an air impeller disposed to deliver air through said inlet to said nozzle means; a bottom of said main housing adapted to support abrasive material thereon; second means coupled to said nozzle means and disposed to cooperate with abrasive material above said bottom; means mounting said housing and said nozzle means rotatably relative to the other; a nozzle forming an outlet for said nozzle means; an aspirator tube communicating with said nozzle and having an open portion carried in close proximity to said abrasive; support means in said housing for holding articles to be cleaned outwardly of said nozzle; drive means for causing relative rotation between said housing and said nozzle means; and means for rotating said impeller to force air through said nozzle means; means forming a transition between said nozzle and said aspirator tube means to create a low pressure or partial vacuum in said aspirator tube means.

References Cited in the file of this patent UNITED STATES PATENTS 1,423,128 Lieatke July 18, 1922 1,849,895 Walters Mar. 15, 1932 1,941,915 Rosenberger Jan. 2, 1934 2,782,564 Liebman Feb. 26, 1957 3,047,986 Mcliulla Aug. 7, 1962 

1. IN AN ABRASIVE CLEANING DEVICE THE COMBINATION OF: A FRAME; A MAIN HOUSING THEREON; AN IMPELLER HOUSING THEREIN AND HAVING AN AIR INLET; AND IMPELLER IN SAID IMPELLER HOUSING; A BOTTOM OF SAID MAIN HOUSING ADAPTED TO SUPPORT ABRASIVE MATERIAL THEREON; A BAR CARRIED BY SAID IMPELLER HOUSING AND DISPOSED TO SCREED AND LEVEL ABRASIVE MATERIAL TO A PREDETERMINED SURFACE LEVEL ABOVE SAID BOTTOM; MEANS MOUNTING ONE OF SAID HOUSINGS ROTATABLE RELATIVE TO THE OTHER; NOZZLE MEANS FORMING OUTLETS FOR SAID IMPELLER HOUSING; ASPIRATOR TUBE MEANS COMMUNICATING WITH SAID NOZZLE MEANS AND HAVING AN OPEN PORTION CARRIED IN CLOSE PROXIMITY TO SAID SURFACE LEVEL OF SAID ABRASIVE; SUPPORT MEANS IN SAID HOUSING FOR HOLDING ARTICLES TO BE CLEANED OUTWARDLY OF SAID NOZZLE MEANS; MEANS FOR DRIVING ONE OF SAID HOUSINGS ROTATABLE AT A LOW SPEED RELATIVE TO THE OTHER HOUSING; AND MEANS FOR ROTATING SAID IMPELLER AT A RELATIVELY HIGH SPEED IN SAID IMPELLER HOUSING. 